Modern printers use a variety of inks to generate images from data. These inks may include liquid ink, dry ink, also know as toner, and solid ink. So-called “solid ink” refers to ink that is loaded into a printer as a solid, which is typically in stick or pellet form. The solid ink is melted within the printer to produce liquid ink that is supplied to a print head for ejection onto media or an intermediate member to generate a printed image from image data. These solid ink printers typically provide more vibrant color images than toner or liquid ink jet printers.
A schematic diagram for a typical solid ink imaging device is illustrated in FIG. 1. The solid ink imaging device, hereafter simply referred to as a printer 110, has an ink loader 112 that receives and stages solid ink sticks. The ink sticks progress through a feed channel of the loader 112 until they reach an ink melt unit 120. The ink melt unit 120 heats the portion of an ink stick impinging on the ink melt unit 120 to a temperature at which the ink stick melts. The liquefied ink is supplied to one or more print heads 130 by gravity, pump action, or both. Printer controller 180 uses the image data to be reproduced to control the print heads 130 and eject ink onto a rotating print drum or image receiving member 140 as image pixels for a printed image. Media 170, such as paper or other recording substrates, are fed from a sheet feeder 160 to a position where the image on the drum 140 can be transferred to the media. To facilitate the image transfer process, the media 170 are fed into a nip between the transfer, sometimes called transfix, roller 150 and the rotating print drum 140. In the nip, the transfix roller 150 presses the media 170 against the print drum 140. An assembly 190 of lever arms, camshafts, cams, and gears urged into motion by an electrical motor responds to signals from the controller 180 to move the transfix roller into and out of engagement with the print drum 140. Offset printing refers to a process, such as the one just described, of generating an ink or toner image on an intermediate member and then transferring the image onto some recording media or another member.
In previously known printers, the transfix roller is moved into and out of engagement with the print drum by the operation of stepper motors coupled to the transfix roller through cams, levers, and/or other force multiplying devices that require a fulcrum or the like. The motor force needed to move moment arms capable of producing 600 to 2200 pounds of total transfix force is substantial. In some cases, more than one motor is required for reliable operation of the transfix roller. Additionally, the cams and levers may also require bearings and springs for proper operation. These mechanical force multiplying components require lubrication and periodic inspection to ensure they are aligned correctly. Noise may also arise from the frictional engagement of the parts with one another. The mechanical interaction of these parts may also limit the speed at which the parts may be moved as repeated movement at faster speeds necessary for higher throughput rates may subject the mechanical parts to higher temperatures and affect the operational life of the components. Consequently, a quieter and simpler mechanism for moving a transfix roller is needed.